Hydraulic extrusion presses

ABSTRACT

A hydraulic extrusion press which has separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the arrangement allowing die loading and unloading to occur simultaneously.

United States Patent 1191 Grant 1 1 June 18, 1974 HYDRAULIC EXTRUSION PRESSES 3,139,183 6/1964 Elkan et a1 207/1 4 1 2 1 1 llwelllorl Gerald Wllllam Glam, Poole, 53111332 351323 32211141 .3831 England 3,156,359 10/1964 Elger et a1. 207/1 3,228,226 1/1966 Elger 72/263 [73] Asslgnee' g' T: g fiF l d 3,241,345 3/1966 Samuel et a1, 72/263 Oumemou amps 3,465,565 9/1969 72/263 [22] Filed: Jan, 31, 1972 3,530,702 9/1970 Ridder 72/263 21 App] 222,04 FOREIGN PATENTS OR APPLICATIONS 1,092,960 11/1967 Great Britain [30] Foreign Prmmy Data Primary Examiner-Charles W. Lanham Feb. 8, 1971 Great Britain 4112/71 Assistant Examiner james Duzan 52 us. (:1. 72/263, 72/253 Agem Firm BriSebiS & Kruger [51] Int. Cl. B2lc 23/00 581 Field Of Search 72/253,263 [57] ABSTRACT A hydraullc extruslon press wh1ch has separate d1e 56] References Cited lqgdijng and unloaclijing sgations (21mg 61 die Carrie; pro- UNITED STATES PATENTS v1 e w1th a num er 0 space e accqmmo anon means, the arrangement allowing d1e loadmg and un- 2,949,05l 8/1960 Hoffmann et al 78/18 loading to occur simultaneously 2,960,220 11/1960 Katko 72/263 2963.15] 12/1960 Kent et a1. 207/1 17 Claims, 4 Drawing Figures HYDRAULIC EXTRUSION PRESSES This invention relates to hydraulic extrusion presses.

In such presses, a billet is placed in a container or pressure chamber, and a pressing stem acting under the influence of an external means, commonly an hydraulic ram, forces the billet material through a die placed at the end of the container bore.

In order to facilitate the removal of the die to a position external of the press, it is known for the die to be mounted in a rotating carrier which may support a plurality of such dies and which is arranged to transfer the dies to and from a single loading/unloading position external of the press to a position on the axis of the said billet adjacent to the bore of the container.

In this construction, whilst the extrusion cycle is proceeding, a die is unloaded from the carrier, transferred to a position external of the press for the necessary cleaning inspection and lubrication and then reloaded into the carrier, unloading and reloading being completed at the same position.

However, on certain types of extrusion where the total cycle time is relatively short, the amount of time required to complete the cleaning inspection and lubrication operations will exceedthe extrusion cycle time. Consequently, there will be a time lag between cycles until the die is again ready for insertion into the press. Furthermore, it will be appreciated that, because the used die assembly has to be removed from the die loading position before a new die assembly can be inserted into the die carrier, there is a further time lag that reduces the time available for press operation.

Furthermore, on presses where a high degree of automation is required, the necessary equipment for unloading, transfer to the die cleaning, inspection and lubrication station, and reloading into the die carrier, be comes increasingly complex.

According to the present invention, there is provided a hydraulic extrusion press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being displaceable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations, respectively. The carrier can be rotatable and conveniently can be rotatably mounted on a press column.

A pair of axially aligned ram assemblies may be arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the rams of said assemblies being movable towards each other. The terms upstream and downstream" are usedithroughout this specification to indicate the position of various press components relative to the direction of extrusion.

The ram of the upstream assembly can, when a die accommodation means is located at the said one station, be passed through the accommodation means. The ram of the downstream assembly can accommodate an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means. The downstream ram may be mounted in a housing incorporating spring means biasing the ram downstream, and the die support rod is biased downstream by spring means incorporated in the ram. The downstream ram and its die support rod may be actuable by means of a pressure cylinder arranged downstream thereof.

Clamping means may be arranged adjacent the upstream end of the downstream rarn assembly which are adapted to retain a die backing ring in position relative to the end of the downstream ram.

Means may be provided for transferring a die unloaded at the unloading station to the loading station, where it can subsequently be reloaded into the carrier in sequence with other or previously unloaded dies. An intermediate die cleaning and inspection station may be provided between the loading and unloading stations through which an unloaded die passes before being reloaded at the loading station. The transfer means may include pivoted chutes arranged at the loading and unloading stations and movable into and away from the working center lines thereof.

Die-holder cleaning means may be provided which can be brought into alignment with the die accommodation means at the unloading station, the said cleaning means being traversible axially to allow the cleaning means to enter a die-holder bore.

Means may be provided at the loading station for transferring a lubricant pad to the upstream face of the die-holder, said means including a pivoted arm for bringing the pad into the loading position, and a pivoted plate adapted to be brought into alignment with the pad, the plate being engageable by the upstream ram to transfer the pad from the am to a die-holder.

The invention further provides a method of unloading a die from a die accommodation means of a press as defined aforesaid, the method including the steps of advancing the die support rod through a die backing ring and into the die until the downstream ram abuts the downstream face of the die backing ring; advancing. the upstream ram into contact with the upstream face of the die so that it is effectively clamped between the two rams; and then further advancing the upstream ram to move the die downstream and out of the accommodation means. The method may include the further steps of advancing the upstream ram until the downstream ram is fully returned, using the clamping means to retain the backing ring in position against the upstream end of the downstream ram advancing. the die support rod to move the die upstream and away from the die backing ring and retracting the die support rod out of the die and at the same time preventing downstream movement of the die.

The invention further provides a method of loading.

a die into a die accommodation means of a press as defined aforesaid, the method including the steps of bringing a die into line with the two rams and adjacent the upstream face of a die backing ring; advancing the die support rod through the ring and into the die; advancing the upstream ram into contact with the upstream face of the die so that it is effectively clamped between the two rams; and then further advancing the downstream ram to move the die and die backing ring.

upstream and into the die accommodation means. The method may include the further steps of removing the backing ring from the die accommodation means by clamping it between the two rams and advancing the upstream ram downstream until the downstream ram is fully returned and then using the clamping means to retain the backing ring in position against the upstream end of the downstream ram, these further steps being carried out prior to bringing the die into line with the two rams.

This invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic part sectional end elevation of part of an hydraulic extrusion press showing a three station die carrier;

FIG. 2 is a sectional side elevation of the press illustrated in FIG. 1; and

FIGS. 2A and 2B are enlarged views of parts of the press shown in FIG. 2, illustrating respectively the die unloading and loading equipment in more detail.

Referring to the drawings, FIG. 1 shows a die carrier 1 which has three arms, the ends of which accommodate die assemblies 2a, 2b, 2c, and which is rotatable about a press column 3 lying parallel to the extrusion axis. As illustrated, die assembly 2a is at position X on the press center line where the extrusion stroke takes place, the direction of extrusion being perpendicular to and entering the plane of FIG. 1; die assembly 2b is at a first external position Y where the used die assembly is removed from the carrier; and die assembly 20 is at a second external position Z where a fresh die assembly may be inserted into the carrier.

As shown in FIGS. 2A and 23, each die assembly comprises a die 4 and a die backing ring 5 mounted in a die-holder 6. On completion of extrusion, the press container (not shown) is moved upstream from the dieholder 6, and the discard separated from the extruded product and stripped from the die, so that the die carrier I is free to be partially rotated anti-clockwise whereby the die assembly 2a moves from its illustrated position at X to external position Y. It will be appreciated that, at the same time the other die assemblies also move and die assemblies 2b and 2c are thus aligned with external position Z and X respectively.

For the sake of clarity, the following description is made with reference only to die assembly 2a, but it will be appreciated that the general sequence described'is equally applicable to the assemblies 2b and 20.

With die assembly 2a at external position Y, the die 4 and die backing ring 5 are removed from the dieholder 6 by co-axial, downstream and upstream ram assemblies 7 and 8 respectively.

Downstream ram 7 is mounted in a housing 9 incorporating a spring 10 designed to return the ram 7 against the end of the housing 9. A die support rod 11 is mounted within the ram 7, and is biased downstream by a spring 12. A hydraulic cylinder/ram assembly 13 incorporating a pusher rod 14 is arranged downstream of the ram 7 and is adapted to drive the die support rod 11 upstream relative to the ram 7 until a shoulder 15 on the rod 14 contacts the ram 7 which is then also moved upstream. The upstream ram 8 is powered by a cylinder 16 and is adapted to be moved downstream.

In operation, the assembly 13 is actuated to advance the die support rod 11 within the orifice of the die 4 until the upstream face of the ram 7 abuts the downstream face of the die backing ring 5, the die 4 and ring 5 being in the full line position as shown in FIG. 2A. The ram 8, under the influence of cylinder 16 is then advanced and holds the die 4 and ring 5 against ram 12.

The ratio of power of the two cylinders 13 and 16 is such that cylinder 16 overcomes cylinder 13 and the die 4 and ring 5 are moved out of the die-holder 6 downstream until a shoulder 17 on the ram 7 abuts the housing 9.

A clamping arrangement 18 is then utilised to retain the die backing ring in position whilst the upstream ram 8 is partially returned. The die support rod 11 is then partially advanced again under the influence of the assembly 13. A shoulder 19 on the rod 11 then contacts the die 4 and it moves it upstream away from the backing ring 5, leaving a gap between the die and the ring into which one side 20 of a chute 21 passes as it rises under the influence of a cylinder ram assembly 22.

The return of the die support rod 11 by the spring 12 allows the die to roll freely down the chute 21 as indicated by arrows 23 in FIG. 1 into a die cleaning station 24 which may be of any desired type and may be either manually or mechanically operated. The die ring 5 will then be in the position illustrated in dotted lines in FIG. 2A.

Cleaning means for the die-holder bore 25 and recess 25a which will now be empty, are now utilised, a brush 26 having arms 27 capable of opening out under centrifugal force being inserted in the bore 25. The brush is suitably mounted on a roller bearing supported shaft 28 driven by a motor 29 through a driving belt 30. The brush is mounted on an axially traversible pendulum arm 31 arranged to move from an inoperative position shown in FIG. 1 into alignment with the die-holder when required. In operation, the brush is axially traversed into the die-holder 6 by a cylinder ram assembly 32.

Other alternative brush units may be used and it is possible to arrange for the ram 8 to incorporate the brush unit thus obviating the necessity for the pendulum arm shown. In this case the die-holder bore 25 can be cleaned either during or after the removal of the die assembly downstream of the die-holder 6 by ram 8.

After cleaning, the ram 8 is returned to the position illustrated in FIG. 2A, the clamping arrangement 18 released and the ram 7 advanced until the ring 5 is remounted in the die-holder 6, whereupon the rod 1 1 and the ram 8 are fully returned. The ring 5 is retained in the holder 6 by suitable means such as a spring ring 33.

The die carrier 1 is then rotated, anti-clockwise, as seen in FIG. 1, after extrusion has been completed at position X, and the ring 5 is brought to position Z where a pair of co-axial downstream and upstream ram assemblies are mounted. The latter mentioned ram assemblies are similar in construction and operation to the assemblies 7 and 8, and consequently they are identified in the drawings as 7 and 8' respectively and all similar and associated parts thereof have been given corresponding primed reference characters.

A cleaned or fresh die 4, which need not necessarily be the same die removed previously at the unloading station is received at the loading position Z from the die cleaning station 24 via a chute 34 operated by cylinder ram assembly 35.

In operation, the ram of cylinder 13' actuates the die support rod 11 which is advanced within the orifice of the die backing ring 5 until the upstream face of ram 7 abuts the downstream face of the die backing ring 5. The ram 8 under the influence of cylinder 16' is then advanced downstream and holds the die ring 5 against the ram 7'. The ratio of power of the two cylinders 16' and 13' is such that cylinder 16' overcomes cylinder 13' and the ring 5 is moved out of the die-holder 6 downstream until a shoulder 17' on the ram 7' abuts the housing 9'. A clamping arrangement 18' is then used to retain the ring 5 in the dotted line position shown in the lower half of FIG. 2, and in FIG. 2B, whilst the ram 8' is partially returned.

A chute 34 carrying the cleaned or fresh die 4', is then raised into alignment with the die-holder bore 25. The die support rod 11 is advanced by assembly 13' through the ring 5 until the tip of the rod is within the die orifice and thus supporting the die. The chute 34 is then lowered and ram 8' advanced to hold the die 4' and ring 5 against the ram 7 Ram 7 is then advanced upstream and cylinder 16' opened to exhaust so that the die 4' and ring 5 are returned into the holder 6 (as shown in full lines in FIG. 2) where they are retained by the spring ring 33.

The rams 7 and 8 are then returned to their original positions and the carrier 1 rotated to bring the new die 4 to the press centerline X.

However, in the extrusion of certain materials, it is desirable that the die face be suitably lubricated before extrusion may commence, e.g., in the extrusion of steel it is known for discs of agglomerated glass powder to be attached to the die face when the die is out of the press. This operation is usually carried out by hand but in the context of a highly automated plant, it is desirable that some mechanical means be provided to obviate the presence of manual labour at this point and in particular, the necessary layout of the equipment described for die changing makes the presence of a man in this area not only difficult to arrange but also physically hazardous.

Therefore, before the die carrier 1 is rotated back into the extrusion position X, a lubricant pad 36 is received froma conveyor 37 by a transfer device 38 operated by cylinder/ram assembly 39. The transfer device 38 is pivoted about an axis point 40 and the pad 36 brought into alignment with the die 4'. Also pivoted about the same axis point 40 is a plate 41 mounted on a counterbalanced arm 42 which is able to pivot about a further point 43. Thus, when the lubricant pad 36 and the plate 41 are aligned with the die 4', the ram 8 is again advanced and pushes the plate 41 against the pad 36 which is transferred from the carrier 38 to the recess 25a in the die-holder 6.

The pad 36 may be retained within the recess 44 either by the fit of the pad within the recess or by a resilient ring, not shown, mounted around the pad periphery.

It will be appreciated that by using the arrangement described above, the dependence of the press cycle time on the rapidity of die cleaning and inspection has beeen eliminated and that the time required for loading and unloading of the die has been reduced as these two operations may now occur simultaneously at their respective external positions. Furthermore, the complexity of the equipment associated with die handling has beeen reduced by making use of separate positions for die loading and unloading.

It will also be appreciated that this design may conveniently be used on all formats of hydraulic extrusion presses, particularly those designed for high production where a plurality of containers are employed instead of the single container mentioned previously.

It will be further appreciated that the direction of rotation and the respective positions of the loading and unloading may be altered to suit the desired method of operation.

The arrangement described above may be modified to incorporate a die carrier having additional die holding positions and/or external positions. By way of example, it may be considered desirable to provide apparatus whereby minor corrections can be made to the die orifice with the die in the die carrier. In this case, the die could be inspected at a first position and ejected if beyond immediate repair; at a second position, if the die has not been ejected, the die could be trimmed or corrected; at a third position, a replacement die could be inserted in the carrier, if necessary, and the die carrier could then be again partially rotated to bring the die once more to the press centreline.

The method of die unloading described above can also be modified. Thus, for example, instead of separating the die from the die backing ring at the unloading station and then passing only the die to the die cleaning station, both the die and the backing ring could be passed together to that station. The die could then be separated from the ring and cleaned as before, the die and ring being subsequently reloaded into the dieholder at the loading station in sequence with other or previously unloaded dies and backing rings.

I claim:

1. A hydraulic extrusion press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the rams of said assemblies being movable, towards each other, from an idle position to a first position in which a die assembly is clamped therebetween, and in the same direction, from said first position to a second position axially spaced from said first position.

2. A hydraulic extrusion press as claimed in claim 1, in which the ram of the upstream assembly can, when a die accommodation means is located at the said one station, be passed through the accommodation means.

3. A hydraulic extrusion press as claimed in claim 2 in which the ram of the downstream assembly accommodates an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means.

4. A hydraulic extrusion press as claimed in claim 3, in which the downstream ram is mounted in a housing incorporating spring means biasing the ram downstream, and the die support rod is biased downstream by spring means incorporated in the ram.

5. A hydraulic extrusion press as claimed in claim 4, in which the downstream ram and its die support rod are actuable by means of a pressure cylinder arranged downstream thereof.

6. A hydraulic extrusion press as claimed in claim 1, in which the carrier is rotatably mounted on a press column.

7. A hydraulic extrusion press as claimed in claim 1, in which clamping means are arranged adjacent the upstream end of the downstream ram assembly which are adapted to retain a die backing ring in position relative to the end of the downstream ram.

8. A hydraulic extrusion press as claimed in claim 1, in which means are provided for transferring a die unloaded at the unloading station to the loading station, where it can subsequently be reloaded into the carrier in sequence with other or previously unloaded dies.

9. A hydraulic extrusion press as claimed in claim 8, in which a die cleaning and inspection station is provided between the loading and unloading stations through which an unloaded die passes before being reloaded at the loading station.

10. A hydraulic extrusion press as claimed in claim 8, in which said transfer means includes pivoted chutes arranged at the loading and unloading stations and movable into and away from the working centrelines thereof.

11. A hydraulic extrusion press as claimed in claim 1, in which die-holder cleaning means are provided which can be brought into alignment with the die accommodation means at the unloading station, the said cleaning means being traversible axially to allow the cleaning means to enter a die-holder bore.

12. A hydraulic extrusion press as claimed in claim 1, in which means are provided at the loading station for transferring a lubricant pad to the upstream face of the die-holder, said means including a pivoted arm for bringing the pad into the loading position, and a pivoted plate adapted to be brought into alignment with the pad, the plate being engageable by the upstream ram to transfer the pad from the arm to a die-holder.

13. A method of loading or unloading a die assembly in a hydraulic extrusion press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the method including the steps of locating a die accommodation means at the loading or unloading station, moving the rams of said axially aligned ram assemblies towards each other from an idle position to a first position in which a die assembly is clamped therebetween and then moving the rams in the same direction to a second position axially spaced from said first position.

14. A method of unloading a die assembly in a hydraulic press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the ram of the downstream ram assembly accommodating an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means, the method including the steps of locating a die accommodation means at the unloading station, advancing the die support rod through a die backing ring and into the dieuntil the downstream ram abuts the downstream face of the die backing ring; advancing the upstream ram into contact with the upstream face of the die so that it is effectively clamped between the two rams; and then further advancing the upstream ram to move the die downstream and out of the accommodation means.

15. A method as claimed in claim 14, including the further steps of advancing the upstream ram until the downstream ram is fully returned, using clamping means to retain the backing ring in position against the upstream end of the downstream ram, advancing the die support rod to move the die upstream and away from the die backing ring and retracting the die support rod out of the die and at the same time preventing downstream movement of the die.

16. A method of loading a die assembly in hydraulic press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the ram of the downstream ram assembly accommodating an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means, the method including the steps of locating a die accommodation means at the loading station to bring a die into line with said axially aligned rams and adjacent the upstream face of a die backing ring; advancing the die support rod through the ring and into the die; advancing the upstream ram into contact with the upstream face of the die so that it is effectively clamped between the two rams; and then further advancing the downstream ram to move the die and die backing ring upstream and into the die accommodation means.

17. A method of loading as claimed in claiim 16, in which prior to the steps listed therein the backing ring is removed v from the die accommodation means by clamping it between the two rams and advancingv the upstream rarn downstream until the downstream ram is fully returned and then using clamping means to retain the backing ring in position against theupstream end of the downstream ram. 

1. A hydraulic extrusion press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rOtatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the rams of said assemblies being movable, towards each other, from an idle position to a first position in which a die assembly is clamped therebetween, and in the same direction, from said first position to a second position axially spaced from said first position.
 2. A hydraulic extrusion press as claimed in claim 1, in which the ram of the upstream assembly can, when a die accommodation means is located at the said one station, be passed through the accommodation means.
 3. A hydraulic extrusion press as claimed in claim 2 in which the ram of the downstream assembly accommodates an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means.
 4. A hydraulic extrusion press as claimed in claim 3, in which the downstream ram is mounted in a housing incorporating spring means biasing the ram downstream, and the die support rod is biased downstream by spring means incorporated in the ram.
 5. A hydraulic extrusion press as claimed in claim 4, in which the downstream ram and its die support rod are actuable by means of a pressure cylinder arranged downstream thereof.
 6. A hydraulic extrusion press as claimed in claim 1, in which the carrier is rotatably mounted on a press column.
 7. A hydraulic extrusion press as claimed in claim 1, in which clamping means are arranged adjacent the upstream end of the downstream ram assembly which are adapted to retain a die backing ring in position relative to the end of the downstream ram.
 8. A hydraulic extrusion press as claimed in claim 1, in which means are provided for transferring a die unloaded at the unloading station to the loading station, where it can subsequently be reloaded into the carrier in sequence with other or previously unloaded dies.
 9. A hydraulic extrusion press as claimed in claim 8, in which a die cleaning and inspection station is provided between the loading and unloading stations through which an unloaded die passes before being reloaded at the loading station.
 10. A hydraulic extrusion press as claimed in claim 8, in which said transfer means includes pivoted chutes arranged at the loading and unloading stations and movable into and away from the working centrelines thereof.
 11. A hydraulic extrusion press as claimed in claim 1, in which die-holder cleaning means are provided which can be brought into alignment with the die accommodation means at the unloading station, the said cleaning means being traversible axially to allow the cleaning means to enter a die-holder bore.
 12. A hydraulic extrusion press as claimed in claim 1, in which means are provided at the loading station for transferring a lubricant pad to the upstream face of the die-holder, said means including a pivoted arm for bringing the pad into the loading position, and a pivoted plate adapted to be brought into alignment with the pad, the plate being engageable by the upstream ram to transfer the pad from the arm to a die-holder.
 13. A method of loading or unloading a die assembly in a hydraulic extrusion press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion Axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the method including the steps of locating a die accommodation means at the loading or unloading station, moving the rams of said axially aligned ram assemblies towards each other from an idle position to a first position in which a die assembly is clamped therebetween and then moving the rams in the same direction to a second position axially spaced from said first position.
 14. A method of unloading a die assembly in a hydraulic press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the ram of the downstream ram assembly accommodating an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means, the method including the steps of locating a die accommodation means at the unloading station, advancing the die support rod through a die backing ring and into the dieuntil the downstream ram abuts the downstream face of the die backing ring; advancing the upstream ram into contact with the upstream face of the die so that it is effectively clamped between the two rams; and then further advancing the upstream ram to move the die downstream and out of the accommodation means.
 15. A method as claimed in claim 14, including the further steps of advancing the upstream ram until the downstream ram is fully returned, using clamping means to retain the backing ring in position against the upstream end of the downstream ram, advancing the die support rod to move the die upstream and away from the die backing ring and retracting the die support rod out of the die and at the same time preventing downstream movement of the die.
 16. A method of loading a die assembly in hydraulic press having separate die loading and unloading stations and a die carrier provided with a number of spaced die accommodation means, the carrier being rotatable so that each die accommodation means can be successively placed in line with the extrusion axis, the arrangement being such that when a first die accommodation means is in line with the extrusion axis, a second and third die accommodation means are located at said die loading and unloading stations respectively, a pair of axially aligned ram assemblies being arranged at at least one of the said stations so that when a die accommodation means is located thereat, one assembly is on the downstream and the other on the upstream side thereof, the ram of the downstream ram assembly accommodating an axially disposed die support rod which is axially movable relative to the ram and can, when a die accommodation means is located at the said one station, be passed into the accommodation means, the method including the steps of locating a die accommodation means at the loading station to bring a die into line with said axially aligned rams and adjacent the upstream face of a die backing ring; advancing the die support rod through the ring and into the die; advancing the upstream ram into contact with the upstream face of the die so that it is effectively clamped beTween the two rams; and then further advancing the downstream ram to move the die and die backing ring upstream and into the die accommodation means.
 17. A method of loading as claimed in claiim 16, in which prior to the steps listed therein the backing ring is removed v from the die accommodation means by clamping it between the two rams and advancing the upstream ram downstream until the downstream ram is fully returned and then using clamping means to retain the backing ring in position against theupstream end of the downstream ram. 